1. Field of the Invention
The present invention relates to the technical field of extracorporeal treatment of blood by an artificial kidney. More particularly, the present invention relates to a device and a method for measuring the ultrafiltration quantity.
2. Description of the Related Art
Patent Application No. EP 213,050 describes a device that permits measurement of the ultrafiltration of blood by measuring the quantity of liquid extracted from the dialysis liquid circuit by an ultrafiltration pump. The device consists essentially of two containers each having a measurement probe capable of indicating when a predetermined level is reached in each of the containers. Each container is filled with liquid pumped by a pump. A set of valves, controlled by a control element are arranged to fill one container while simultaneously emptying the other container, and vice versa. The probes send an electrical signal to the control element each time the predetermined level is reached, and the control element, knowing the volume of each container, can then calculate the quantity of ultrafiltrated liquid. However, a drawback to the above-identified device is that it lacks precision in situations where the pumped liquid contains bubbles. Such bubbles interfere with level detection by the measurement probes.
In addition, the above-described device loses precision as the filling rate of the containers increases. In situations where the measured liquid is conveyed by a pulsed ultrafiltration pump, liquid level detection is disturbed.
An object of the present invention is to overcome the disadvantages of the prior art and to provide a device and a method for measuring ultrafiltrate that eliminates the presence of bubbles in the liquid extracted the dialysis liquid circuit.
Another object of the present invention is to provide a device and a method for measuring the ultrafiltrate which are not as sensitive to pulsations in the liquid being measured.
A further object of the present invention is to provide a device and a method for measuring ultrafiltrate wherein the filling rate of the containers can be reduced as the liquid approaches the level-detection devices.